Demonstrations have taken place in about a dozen towns around Spain with a large protest due to take place in the capital on Saturday evening.

Tens of thousands of anti-war protesters have marched in Rome with similar events being held throughout the world including Sydney and Tokyo.

Riot police were deployed at rallies in India, Egypt, Turkey and the Philippines.

Big Ben

Police said the two Greenpeace protesters scaled Big Ben at 0615 GMT, unfurling a banner saying "Time for Truth".

Police arrested the two men - named by the group as brothers Harry and Simon Westaway from Lewes in Sussex - and responded to the breach of security by saying they were confident they "would not have been able to access inside the Palace of Westminster itself".

Greenpeace said they did not encounter any security in getting over two fences and climbing the tower.

The group sent another volunteer to the front gate of the site to inform police it was a "peaceful protest and not a terrorist attack".